CVE-2026-105887

Executive Summary

CVE-2026-105887 is a stored cross-site scripting (XSS) vulnerability in the Robo Gallery WordPress plugin, affecting versions up to and including 5.1.6. The flaw stems from improper neutralization of user-supplied input during web page generation, allowing an authenticated attacker with low privileges to inject persistent malicious scripts. Successful exploitation can lead to session hijacking, credential theft, or arbitrary actions in the context of an administrator's browser, constituting a significant risk for WordPress sites using this plugin.

Technical Analysis

The vulnerability is classified as CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'). In the context of the Robo Gallery plugin, this indicates that one or more input fields—likely related to gallery management, image metadata, or shortcode attributes—fail to properly sanitize or escape user-controlled data before rendering it into HTML pages. Because the vulnerability is specifically identified as stored (persistent) XSS, the malicious payload is saved to the backend database (e.g., within the WordPress posts, postmeta, or options tables) and later served to any user viewing the affected gallery or page. The CVSS vector CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L indicates network exploitable, low attack complexity, low privileges required, and user interaction needed. The scope change (S:C) implies the vulnerable component (the plugin) can affect resources beyond its security scope, such as the WordPress administrative interface. The NVD description does not specify the exact parameter or function name involved; therefore, the precise injection point (e.g., a gallery title, description, custom CSS field, or shortcode attribute) cannot be confirmed from available data. However, the attack surface is limited to authenticated users with the ability to create or edit Robo Gallery content, which in default WordPress configurations includes Contributor-level users and above. The lack of a patch (0/4 patch confidence) means the flaw remains unaddressed in the current codebase.

Exploitation Scenarios

1. Reconnaissance and Target Identification: An attacker identifies WordPress sites running the Robo Gallery plugin version 5.1.6 or earlier. This can be done via Shodan dorks (e.g., http.html:"wp-content/plugins/robo-gallery") or by scanning public plugin directories. The attacker registers or compromises a low-privileged account on the target site (e.g., Subscriber or Contributor, depending on the plugin's capability requirements for gallery creation).

2. Triggering the Flaw Class: The attacker navigates to the Robo Gallery management interface and supplies malicious JavaScript within any input field that is stored and later rendered without proper output encoding. Due to the stored XSS nature, the payload persists in the database. No specific field names are disclosed in the NVD description; therefore, the attack is described at the vulnerability-class level: the attacker injects a script payload into a plugin-managed input that is not neutralized during web page generation.

3. Payload Execution Method: Once the crafted gallery is published or embedded, any user who views the affected page—including administrators—executes the injected script in their browser. This occurs because the plugin outputs the stored input directly into the HTML response without escaping. The payload could be a simple <script> tag or an event handler that steals cookies, performs actions on behalf of the victim, or redirects to a malicious site.

4. Post-Exploitation Impact: With the ability to run arbitrary JavaScript in the context of an administrator, the attacker can hijack sessions, create new administrative accounts, install backdoors, modify site content, or exfiltrate sensitive data. Given the scope change (S:C), the compromise extends beyond the plugin to the entire WordPress installation and potentially the underlying server, depending on the administrator's permissions. No public proof-of-concept or exploit code is available; the attack chain is inferred from the vulnerability class.

Impact Assessment

The CVSS score of 6.5 (Medium) reflects a moderate severity. The vector indicates that exploitation requires network access (AV:N), low complexity (AC:L), low privileges (PR:L), and user interaction (UI:R). The scope change (S:C) elevates the risk because the vulnerable component can affect the broader WordPress ecosystem. Confidentiality, integrity, and availability impacts are each rated Low (C:L/I:L/A:L), but the persistent nature of stored XSS means that successful exploitation can lead to widespread compromise if an administrator views the malicious content. Business impact includes potential data breaches, website defacement, loss of customer trust, and regulatory penalties. The blast radius encompasses all users who access the affected gallery, with the most severe consequences reserved for administrators. No known active exploitation or threat actor campaigns have been reported, and the EPSS score is not yet available.

Detection Guidance

Sigma Rule

title: Stored XSS in Robo Gallery Plugin
id: 8f4d3e2a-1b5c-4d7e-9f0a-2c3b4d5e6f7a
status: experimental
description: Detects potential stored XSS attempts via the Robo Gallery WordPress plugin (CVE-2026-105887)
author: Threat Intelligence
date: 2026-01-01
logsource:
  category: webserver
  product: apache
  service: access_combined
detection:
  selection:
    cs-method: 'POST'
    cs-uri-query|contains: '/wp-admin/admin-ajax.php'
    cs-uri-query|contains: 'robo_gallery'
  keywords:
    - '<script>'
    - 'onerror='
    - 'onload='
    - 'javascript:'
  condition: selection and keywords
falsepositives:
  - Legitimate administrative activity with benign scripts
level: medium
tags:
  - attack.t1059.007
  - cve.2026.105887

### YARA Rule
```yara
rule CVE_2026_105887_Robo_Gallery_Stored_XSS
{
    meta:
        description = "Detects stored XSS payloads in Robo Gallery plugin content"
        author = "Threat Intelligence"
        date = "2026-01-01"
        reference = "CVE-2026-105887"
        severity = "medium"

    strings:
        $xss1 = "<script>" ascii wide nocase
        $xss2 = "onerror=" ascii wide nocase
        $xss3 = "onload=" ascii wide nocase
        $xss4 = "javascript:" ascii wide nocase
        $gal = "robo-gallery" ascii wide nocase

    condition:
        $gal and any of ($xss*)
}

Suricata IDS Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-105887 Robo Gallery Stored XSS Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"robo_gallery"; http_uri; content:"<script"; http_client_body; nocase; reference:cve,2026-105887; classtype:web-application-attack; sid:10000001; rev:1;)

Elastic Detection

sequence by host.id, user.name with maxspan=5m
  [ network where network.protocol == "http" and http.request.method == "POST" and
    url.path == "/wp-admin/admin-ajax.php" and url.query contains "robo_gallery" ]
  [ network where network.protocol == "http" and http.request.method == "POST" and
    url.path == "/wp-admin/admin-ajax.php" and url.query contains "robo_gallery" and
    (http.request.body contains "<script" or http.request.body contains "onerror=" or http.request.body contains "javascript:") ]

Splunk SPL Query

index=web sourcetype=access_combined
method=POST uri_path="/wp-admin/admin-ajax.php" uri_query="*robo_gallery*"
| search form_data="*<script*" OR form_data="*onerror=*" OR form_data="*javascript:*"
| stats count by src_ip, uri_path, form_data
| where count > 0

Wazuh OSSEC Rule

<group name="web,appsec,">
  <rule id="100100" level="10">
    <decoded_as>web-accesslog</decoded_as>
    <field name="url">/wp-admin/admin-ajax\.php\?.*robo_gallery</field>
    <field name="method">POST</field>
    <field name="request_body">\<script|onerror=|onload=|javascript:</field>
    <description>CVE-2026-105887: Potential stored XSS attempt against Robo Gallery plugin</description>
    <mitre>
      <id>T1059.007</id>
    </mitre>
    <group>cve_2026_105887,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate Mitigations:

   • Disable or uninstall the Robo Gallery plugin if it is not business-critical.
   • If the plugin must remain active, restrict creation and editing of galleries to trusted administrator accounts only.
   • Implement a Web Application Firewall (WAF) rule to block script tags and event handlers in POST requests to admin-ajax.php or any plugin-specific endpoints.
   • Conduct a manual review of existing gallery content for injected scripts and remove any suspicious entries.

2. Patch/Upgrade Steps:

   • Monitor the official Robo Gallery plugin page and vendor channels for a security update. As of this report, no patch is available.
   • Once a patched version is released, immediately update to the latest version and verify that the vulnerability is resolved.

3. Long-term Hardening:

   • Enforce the principle of least privilege for WordPress user roles; avoid granting Contributor or higher privileges to untrusted users.
   • Regularly perform security audits of all installed plugins and themes.
   • Deploy a Web Application Firewall with virtual patching capabilities to protect against known and unknown XSS vectors.
   • Educate content managers about the risks of XSS and the importance of validating user input.

References

• NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-105887
• CWE-79: https://cwe.mitre.org/data/definitions/79.html
• MITRE ATT&CK T1059.007: https://attack.mitre.org/techniques/T1059/007/
• WordPress Plugin Security: https://wordpress.org/plugins/robo-gallery/
• No known threat actor campaigns or exploit-in-the-wild evidence at this time.